Velcro v Pin Pull Force

[imported_Mac]

Has anyone done any testing and have figures on the differences in the force needed to open pin v velcro?

After some "hand / feel" testing I know that pin (generally) have a lower force required to open the container before extraction - but I would be interested in the actual figures relating to this.

Thanks for any info........

[imported_Tom Aiello]

I measured pull forces with pin and velcro, using a spring scale, in various body positions, a while back (actually, I habitually do this whenever I buy a new rig, too). Here's what I found:

1) Velcro rigs average around 18 pounds of force to open when fully closed. Priming the velcro can reduce the required pull force by as much as you want.

2) Pin rigs with standard loops average around 12 pounds of force to open.

3) Pin rig opening force is much more variable than velcro opening force. I've never tested a velcro rig (properly closed, with decent velcro) that took less than 14 pounds of pressure, or more than 22 pounds of pressure (in any configuration). I've been able to get pin rig opening force down to 2 pounds (using loose spectra closing loops) and up to about 20 pounds. In addition to being more sensitive to differences in the pack job (and, of course, loop length), the pin rigs appear to be more sensitive to changes in body position (I've seen a hard tuck increase pin pull force by as much as ten pounds). Velcro pull force, on the other hand, seems mostly determined by the strength of the velcro (and design of the particular rig), with pack job and body position playing less of a role.

4) Velcro opening force tends to decrease with other circumstances, whereas pin pull force tends to increase. In other words, if the highest pull force you measure on your velcro rig, at home on the floor, is 18 pounds, you can pretty much guarantee that the velcro will open before or at 18 pounds of force under almost any circumstances.

5) Pin opening force on the other hand, tends to increase with changing circumstances. So a pin rig that you test to open at 8 pounds at home could take as much a 20 pounds to open in the field (say, if you pitch head high, with a tight tuck flap closure and while curled into a tight tuck).

Bottom line? Pins are more variable, and take greater attention to detail, but can be useful in some special circumstances where either (a) low pull force is desirable, or (b) high speed airflow might peel velcro.

Also, have you dug through the archives?

Have a look at this thread:

http://www.blincmagazine.com/forum/d...2&topic_id=603

The relevant part:

> 1) The highest force exerted on the break cord was at the moment that the rig reached bridle stretch (i.e. first impact with with the shrivel flap) for a Velcro rig (I used my Vision). This was typically around 25 lbs of pressure. By priming the velcro, I was able to reduce the pull force at this point to approximately 10 pounds. Priming to less pull force left me with a shrivel flap that I did not consider adequately closed to exit with. For comparison purposes, the same rig pulled the shrivel flap with approximately 15 pounds of pressure in a floor test (standing, sitting or laying and having someone else just pull the shrivel flap). The force exerted at this point with my pin rig (Prism) was approximately 10 pounds. The pin rig pull force was consistent with the bridle routed under the tuck flap or outside of it--the tuck flap did not increase the pull force.



--Tom Aiello
tbaiello@mac.com

[imported_Mac]

cheers Tom! that was helpful...........

has anyone thought of linking this to 689's PC' drag table?

I would be interested in the time / distance it takes on different PC's and containers - I still think that the difference in a 46" and a 42" ( on 0-1 sec delay) is minimal after some testing we have done in the 200ft freefall region - on some occasions the 42 extracts quicker (same delay, same pin rig, supposed same packing and pin tension) - I have heard of someone taking a sub-200 with a 42 and I myself have freefallin a 42 on a 250ft (2 second delay) and 220ft (1 second delay) ....without much difference in opening height (visual not lasered) when i have done the same with a 46...... so i am just trying to find some answers to some questions i have...........

This is why i am looking at 689's table and wondering about pin v velcro tensions.............


thanks for any help!

Michael